SIMV may decrease lung injury in small infants. An abdominal pressure capsule (e.g., the Star Sync-(TM) trigger) is the most reliable type of trigger for this population, since flow and pressure triggers become increasingly unreliable with decreasing weight. Even the pressure capsule trigger has limitations. In Phase 1 we demonstrated the feasibility that an acoustic respiratory motion sensor (ARMS) could improve the performance of, or replace, the capsule trigger sensor. In Phase 2 we will develop and test an ARMS prototype trigger. Phase II Specific Aims are 1) to obtain ARMS response data on 10 larger infants so the distribution of patient weights resembles that encountered in clinical practice; 2) Devise algorithms for an ARMS-plus-capsule and an ARMS-only trigger and incorporate them into a hardware prototype trigger; 3) Evaluate relative performance of the two ARMS triggers and pick on for continued development via extended recordings in 10 pre-term infants ventilated by a Star SyncTM controlled Infant Star with the ARMS prototypes running simultaneously (but not controlling the ventilator); 4) Demonstrate improvement in gas exchange between the ARMS-plus-capsule prototype trigger (or equivalency of ARMS-only trigger) and Star SyncTM in a blinded crossover study in 24 preterm infants; 5) Develop specifications for a limited production of ARMS triggers for use in later multi-center collaborative trial PROPOSED COMMERCIAL APPLICATION: Potential commercial applications include: 1) an improved ventilator trigger for infant SIMV, 2) a trigger for non-invasive patient synchronized ventilation of both infants and adults. Jaycor has provided IR&D funding for development of the prototype device and obtaining the pilot data. In addition, Jaycor has committed the equivalent of over $90,000 in labor to performance of the Phase I and Phase II effects. Jaycor will collaborate with Mallinckrodt in developing the improved ventilator trigger.